Alternating-current-motor control.



J.D.IHLDER. ALTERNATING CURRENT MOTOR'OONTROL.

APPLICATION FILED JAN. 15, 1907. 982,067. Patented Jan. 17,1911.

3 SHEETS-SHE ET 1.

. WITNESSES: INVENTOR mm a GM,

j (27% ATTORNEY J. D. IHLDBR.

ALTERNATING CURRENT MOTOR CONTROL.

APPLICATION rILnn JAN.15, 1907.

982,067, Patented Jan. 17,1911.

3 SHEETS-SHEET 2.-

wmwesses: 1 1 Y 'INVENIOR I 744 W ATTORNEY J.D.IHLDBR.

ALTEBNATING CURRENT MOTOR CONTROL.

APPLICATION FILED JAN.15. 1907.

" 982,067; I I Pate11ted Jan. 17,1911.

3 sums-sum a.

at 7 5 o ATTORNEY UNITED sTATEs PATENT OFFICE.

JOHN D. IH LDER, OF NEW YORK, N. Y., ASSIGNOE TQ OTIS ELEVATOR COMPANY,OF

JERSEY CITY, NEW JERSEY, A CORPOEATHIN OF NEW JERSEY. I

ALTERNATING-CURRENT-MOTOR CONTROL.

To all wlwm it may concern:

Be it known that I, JOHN D. IHLDER, a

citizen of the United States, residing in New York city, in the countyof New York and State of New York, have invented a new and usefulImprovement in Alternatin Current-Motor Control, oi; which the followingis a specification. 1

,My invention relates to alternating current'motor controllingapparatus, and one of its objects is to provide means for auto-.

matically cutting out or short-circuiting the starting resistance whichdepends for its operation upon the varying current strength of-the motorcircuits.

Another object of my invention is to provide means for acceleratinganalternating current motor from a state of rest to full normal speed,which shall be automatic in its operation and dependent uponthe loadonthe motorztf My invention relates to a construction and arrangement inwhich one or moremagnets in the rotor or stator circuit of an alternatmgcurrent motor are arranged to control a series of switches which, whenclosed, short-- circuit-the starting resistance, and they ,aresodesigned that the rush of current upon starting the motor issufiicient to cause them to open their contacts, thereby inserting thestarting resistance in the motor circuit. As

I the motor picks up speed, the current therein gradually decreases andthe magnets are sufficiently deenergized to enable them to close theircontacts, thereby short circuiting the starting resistance'iinsuccessive steps; In some cases I )rovide. auxiliary resistances to'keepthe initial rush of'starting current within bounds. -Theseauxiliaryresistances are short-circuit'edas soon as the starting resistance hasbeen insertedin the motor circuit The 2;; accompanying drawingsillustrate diagrammatically various ways in which I Specification-ofLetters Patent.

Application filed January 15, 1907.

by the action of gravity. spring or, any equivalent device may be usedPatented Jan. 17, 1911.

serial No. 352,3 82.

accomplish the objects of my invention enumerated above.

Figure 1 illustrates a wiring diagram in which the starting resistancecontrolling magnets are connected in series with the rotor circuitofrthe motor. Fig. 2 is a similar diagram except that the magnets whichcontrol the starting resistance are. in series with the stator windin sof the motor. Fig.

3 is modification o Figs. 1 and 2, the

essential, difference bein that the starting resistance in this caselscontrolled by' a single ma net of the solenoid type which op:

erates a siding contact device. Fig 1: is-a further modification ofFigs. l and 2. In this case two magnets are used to control the startingresistance, each magnet being connected in different phases of thestator circuit. Fig. 5 'is a further modification employing double coilmagnets for controlling the starting resistance, the coils of eachmagnet being connected in different phases of the stator circuit;

For the sake of clearness and easy comprehension, the various magnetsare illustrated as single-phase. magnets of the sole noid type, but Iwish it to be clearly understood that the various magnets employed maybe, of an construction or type suitable.

to the duty w iich they are to perform; For

instance, it is perfectly feasible to usebut one magnet of single ormultiple phase windings operating a number of contacts consecutively forcutting out the starting resistance, or, if desired, a series of singleor multiphase magnets each having one or more con-- tacts. Also anydesirable number of magnets and contacts may be used, depending upon thenumber'of steps into which the starting resistance is sub-divided.

The various agne'ts used to carry but my invention and as illustrated inthe drawings, are of a type which close to close these. contacts, anda-dash-pot or magnetic retarding means could be added if desired. a,

Similar referencecharacters throughout the v'arious figures for similarparts, in which- I 4', b and q desi ing current supp y switch.

ate a source of alternat-l and S is a main line are used their contactsIf desired, a

ibo

' motor;

1, 2 and 3 designate mainline wires leadg to the.contr ll g anpstatusand th Referring'more particularly to Fig. 1; 4 and 5 designate magnetshaving cores'6 and 7 to which are connected contact devices-8f and 9,respectively. The contacbpiece 8 connects or bridges the fixedcontactsl'l and=12; while" the contact-piece 9 bridges the fixedcontacts 13 and*"14*- when inthe position shown. To an extension of the.magnet core 7 is faste neda contact 30 above'whieh is a similar fixed;contact 3l'adapted to be engaged thereby when thecontact 30 is raised bythe. core 7. .10 designates the motor startingresistance and. :1i5designates; a :magnct" having a core 16 to which is connected the.

cantactsIBQ andclt'a'z itVhenft-heecore-glfiis in r ycoil magnetsfforcontrolling thestartmg reits lowermost position; these contacts 132 and,33 are in the positioncshown, but-,i as'soon as the core '16 islitttedg-the: contact 32 engages a fixed contactI8.vandxthe-'contactIl'i engages a fixed contact 832 19, 20l'and 21designate auxiliary resistance 1 .225 is an alternating f current motorthree" collector rings 22," 23' and 24; being s o'wn on the rotorshaftgwhilc 29 is 'a pulley; or otlie'r' power-transmitting device; 26;27 and "28 designate the stator:

net switch a is 'conneeted'by the win- 34. to

c ii if fi manner, 111s wires V 42 eennecetlle poiats respectively." 111like a d a e 'w "and 41 with the eon tacts13 and la. "icspe'ct itfelyfffm le o t-4.0

" the eoll ec'tor ring 2 thepointflt'isfconnected through the resist itoflthe collector ring '22 and the pointi disconnected through thewindingsfof jmagnet,j'switches fl and 5 through-the r istaneejso' t'o it-he collector ."'ringQQflfThe m'aifn' l'iiiel wiresl, 2 :and3leadI1dir'ectly tothe-s'tator terminals'26, 27, and 28.. 'It'f will adnytsen byianfiiis'pectiomof the drawing that the lcontactstf33 and .1 17,

when connected,: shortcir cuit [the resistance 20, and the contacts'18.;anjd-32 gshort-circniit;

the resistanceg21, when; they. arc connected, by the m agnetswitc'h; 15-;Tl1e;c0n tact-s,30

shor ilCllltf the, resistance-19. i The foregoing description appliesequally well to Fig:-.2.=beThe only difference isthat -in'Fig. 2'thema'gnet=switches41-and 5.; have, their windingsconnectednn serieswith one.

phase off the statorlwinding of theiniotor' V i i i worder zto startanalternating current 'm'otor fronirest, endtop'revent a too sudden rushof current,whichwould seriously affect the power 'c ircuit andprobablydamage the ;motor, it lias been found that the best reis bombewas through the-main:- wire j "conta ct-piece'es ore I by {the rod-5151:so"

as the core 47" solenoid winding 44, the contact-piece 4:8 is moved overthe contacts 49, 49. A Contact 46 is also carried by the core 47 and isadapted to engage afixed contact 45 whenever the core 47 is lifted toits uppermost position.

In otherrespects Fig. 3 is similar to Fig. 1. Fig t resembles Fig. 2very closely, the essential-"difference being that while in Fig. 2thestarting resistance controlling magnet switches t and 5" are connectedin series with one phase of the stator circuit, Fig. 4 shows each.magnet switch connected in a separate phase of the stator circuit. Also,the magnet switch 4 in Fig. 4: has an additional contact 52 carried byan extension on its-imagnct core, and cotiperating with a ;fiXed-c0ntact53 placed directly above it. As before stated, Fig.5 comprises doublesistance 10; each'of'the coils ofany one magnet. is connected in serieswith a different phasexofrwthe-stator winding of tlie motor rTheresistance controlling switches, ofsvhieh threeiare shown, aredesignated by the nu-...

merals184,'60 and 85. They are'very similar '1n"construct1on, the chiefdifference being in thG" COI1t1QtS1 operated thereby and .intheele'ctrical-:connectio11s which lead to these contacts. -Each ofthese magnetswitches' comprises two solcnoi cores, asG" aud o,controlled by the windings 72 and 73, re-

'nectcdtogetlier ateither end by 'Y-shapcd insulation pieces 78 and 81.The upper insulation'jpiece 78 carries a contact- 52 adapted to"engagea'*fixed contact 53 situated a short distance above it. The lower insu-"lation' pieoe 'tl is' connected to a contactmakmg device comprising thecontact-piece 8" which engages two fixed contacts 11' and 12, andaeontact 58 which is insulated from theflcontact-piece 8' by the'insulation 57.

'Ihislc'ontact' 58 engages'a fixed contact 59 when in its closedposition, as shown. The sw tch 85,;h'a1si.av single contact-piece 9'attachedftotheinsulation 83 and it bridges two fixed. contacts1'3' and14 when in its. lower I most position; as shown on the drawing.

*snlts'havebeen obtained by placing a resist- ,ance 'in' series'with therotor circuit, this re- ,ill'p-liave. shown throughout the variousscene? sistancc being short-circuited as soon as the motor has reached aproper speed. Theoretically, this starting resistance should be currentto pass in order to enable the motor v to quickly reach normal fullspeed, the means for cutting out the starting resistance which isusually dependent on a time ele ment operates to cut out the resistanceand the motor gets current far in excess of what it should be untilfinally the main fuse blows or the motor is-seriously damaged. Again,

if the motor is very lightly loaded, it is desirable to accelerate itrapidly to full speed in order to prevent too great a loss in the.

turn: Assuming the parts in Fig. 1 as shownand the main line switch Sclosed, current will flow directly to the motor stator through the wires1, 2 and 3. At the same time an induced current will be set up in therotor, connections from which lead to the slip rings 22, 23 and 24. Themagnet switch comprising the magnet 23 is at this time closed and thestarting resistance 10 shortcircuited thereby, since the terminal 40'is'connected to the contact-piece 14 and the terminal is connected to thecontact-piece 8, and since these contactsare in electrical connectionwith each other through the contact-pieces 8 and 9. The auxiliaryresistance 21, however, isin circuit between the slip rings 22 and 23;also the auxiliary resistance 20 is in series with the slip rings '23and 24, the switches controlled by the magnet 15 being open at thistime. As it is frequently desiredto allow the motor when starting underload more current than isfrequired when running at full speed, theauxiliary resistances 20 and 21 are so proportioned as to give therequisite amount, and the motor is enabled to start. magnets 4 and 5arefinseries with the resistance 20' and the slip rings 23 and 24;therefore, the initial starting current in the rotor passes throughtheir windingsand the ma netizing power roduced therein is of an eientstrength to ift their cores and conneeted contacts, thereby insertingthe starting resistance 10 in the rotor circuit, The.

' motor has by this time overcomethe frie-- 765501181 starting load anddoes not require so r The windings of the much starting current. Whenthe magnet 5 separates the contacts 13 and 14 it also connects thecont-acts 30 and 31, thereby shortcircuiting the resistance 19. It willbe noticed that the winding of magnet 15 is in series with theresistance 19 across the main wires 1 and 2. It therefore receivessingle-phase current directly from the mains. The resistance 19,however, is of such amount as to limit the current in the winding ofmagnet switch 15, preventing it from lifting its core 16 and cont-actsconnected there with. As soon, however, as the magnet 5 has connectedthe contacts 30 and 31 the resistance.19 is short-eircuited and themagnet 15 is of sufficient strength to lift its core and connect thecontactslS and 32, and 17 and 33, respectively. The connecting of thesecontacts short-circuits the auxiliary starting resistances 20 and 21.The motor is now receiving normal starting current limited in amount bythe resistance 10.

As the motor accelerates, the current in the motor diminishes, as .doesalso the current in the magnets 4 and 5, they being in thesame circuit.The strength of current in the: windings of magnets 4c and 5 finallyreaches a point at which it will no longer sustain the cores (3 and 7 intheir uppermost positions, and the cores will be gradually released todescend by gravity. The magnet 4 is purposely made weaker than that ofmagnet 5, consequently it will permit its switch to be closed first,thereby cutting out a portion of the starting resistance 10. As soon asthe magnet 5 permits its switch to close, all of the resistance is cutout of the rotor circuit and the motor runs at normal speed at full linepotential. \Vhen themagnet 5 closes its lower switch, the contacts 30,31 ar'eagain separated, thereby reinserting the resistance 19 in ,serieswith the winding of magnet 15; but while the diminished current nowfiowingis not sufficient to lift the core 16 and its connected contacts,it is of ample strength to maintain the core in its upper position.'lherefore, the auxiliary resistances 20 and 21 remain short-circuited.

To stop the motor it is merely necessary to open the main line switch S,whereupon current is cut off from the motor and all the parts return tonormal starting position. It will thus be seen that it is impossible toinjure the motor by excessive starting current since the initial 'rushof current is kept within bounds by the auxiliary resistances 20 and 21and these resistances cannot be short-circuited until the startingresistance has first been" inserted, and the starting resistance itselfcannot be cut out until the motor is in a propercondition to justify heremoval of 85 to the stator of the motoigthe induced circuit, thestarting resistances 50, 50 being short-circuited. The initial startingcurrent lifts the core 47, inserting thestarti'ng reslstance, and byconnecting the contacts 45 and 46, allows the magnet to operate itsswitches and thereby cut out the auxiliary.

resistances and 21, and as the motor speeds up and the rotor currentdecreases, the core 47 gradually lowersandcutsout step by step thestarting resistance 50, 50.

. is at a maximum, the magnet switches 84, 60 and 85 are sufficientlyenergized 'to lift their by cuttin '21 out o The operation of Fig. 4issimilar to the foregoing except that in this instance a contact 52cooperating with aifixed -contact .53,

is connected to the magnet 4; thus it is. manifestly impossible tooperate the magnet 15 unless both the cores of the magnets 4" and 5" arein their uppermost positions,

which insuresthat all of the starting resistance must'be inserted inthe. rotor circuit before it is possible to operate the magnet 15,thereby short-circuiting the auxiliary starting resistances. V

In Fig. 5 the magnet'coils-72, '74 andf76 are in parallel with eachother, and in series with the main wire-3 which is one phase conductorof the stator circuit also the coils '73, and 77 are in parallel seriesrelationto the main 1' which is another phase conductor of the statorcircuit. Upon closing the'main line switch S, current flows from thepower circuit a, b and of through the windings of the magnet switches84,60 and rot r circuit being limited in strength by the aux liary startingresistances 20 and 21",the starting resistance 10 is at this timeshortcircuited by the magnet switches 84, 60 and- 85. Since the statorcurrent upon starting respective cores and connected mechanism, therebyinserting into the rotor circuit the entire starting resistance, 10.which hereto: fore was short-circuited. The switches 84, (30 and are nowin their upper positions andltheir upper contacts 52 53, 62-61,

and 30--31, respectively, are'connected These contacts, when connected,short-cir cuit the resistance 19 since they provide a path around it ofpractically zero resistance. I The winding of the magnet switch beinthereby subjected to the full line potentia existing betwen the phases 1and 3, sufficient magnetism is produced therein to operate this switchto connect its contacts,there-= the auxiliary resistances 20' 8J1d therotor circuit. By this time the motor has icked up its load and receivescurrent limite in amount y the starting resistance 10. At about this imethe current flowing to the stator and the magnet switches 84, 60 and 85has diminished to such an extent that the magnet switches are not ableto longer maintain their cores and connecting mechanism in their raisedposition. The

.coilsof magnet switch 84 being purposely made weaker than those ofswitches 60 and 85, the switch 84 will be the first to connect its lowercontacts and separate the top contacts 52 and 53'. A circuit to themagnet 15 is thereby interrupted at these top contacts,-but the windinof magnet 15 still receives current throu i the resistance 19, and thiscurrent is-of su cient strength to maintain, the switch in a closedposition. The

,magnetswitch 84,having closed itslower contacts, that portion, of thestarting resistance 10 between tl1e.;points35 67, 359-66, i

rises, producing a still further drop in current strength in both therotorand stator circuits. The motor, speed increases until the and,46-.70, isshort circuitedf The'cur'rent in the, rotor is. nowincreased andthe, speed.

magnet-switch 60 is unable to longer maintain its core in its uppermostposltion and the same will dro ,thereby connecting its lower contacts anseparating. the top. contacts 62 and 61. -,The connection of the lowercontacts, causes additional sections of the starting resistance 10 .tobe short-circuited, namely, that-,part of .the resistance 10 between thepoints 67.68, 66-69,and- 7 0.7 1.

The motor further increases its speed until 1 finally the magnet switch85 permits its contacts to be connected, thereby joining t0+,

gether the terminals 35, 46 and 41 of the starting resistance 10. Thiswill of course short-circuit the'entire starting resistance 10 andthemotor quickly reaches full normal speed, there being no appreciableresistance in eitherjthe rotor or stator circuit of the motor. Openingthe main line switch S operates to stop the motor and return all theparts to initial position.

While I have shown and described my device'as' controlling the insertionand cutting out of thestarting resistancein three steps, there maybeonlyone or two steps or more than three steps. The number of divisionsor 'stepsinto which the starting resistance may b"divided is entirelyoptional and depends uponthe's'ize of the motor used and the dutywhichit is to perform. By the use of additional magnet switches orcontacts, or otherwise, both the starting resistance and auxiliaryresistance may be divided into as. manysteps or sections as desired, themain object'being to start and accelerate the motor promptly andsmoothly.

.It should be particnlarl notedthat iitthe main line current should beunintentionally interrupted, or when interrupted by the opening of theswitch S, too much current cannot be received by the motor when thecurrent ,is again turned on. This is for the reason that as soon as thecurrent to the electromagnetic switch is interrupted, the

- contacts 18 and 32 will become disengaged as well as the contacts 30and 31. It is therefore necessary that the starting resistance bereinserted before the auxiliary resistances can be cut out to effect theacceleration of the nibtor initially.

My invention is adapted to an alternating current motor of either singleor-multiphase type, and while I have shown and described a systemembodying my invention using auxilia ry starting resistance, in somecases I prefer to omit them entirely, particularly where the motor to becontrolled is of small size and does not require a heavy startingcurrent to roduce the necessary torque (Bbviously those skilled in theart may make various changes in the details and arrangement of parts ofmy invention without departing from the spirit and scope thereof,', andI desire, therefore, not to be lmited to the recise construction hereindisclosed.

avin thus fully described my invention, what I c aim and desire tohave'protectedby Letters Patent of the United States is 1. Inmotorcont-rolling apparatus, the combination with starting resistance,of auxiliary resistance, means for effecting a successive insertionof-said starting iesistanee and the cutting out'of the same, and adevice for cutting out said auxiliary resistance upon the insertion ofsaid starting resistance.

1 2. In motorcontrolling apparatus, the combination with an alternatingcurrent motor of the induction type, of starting resistance connected tothe secondary of the motor but initially cut out, auxiliary resistanceinitially in circuit with said secondary, means for inserting saidstarting resistance" when the motor receives current, and appliancesdependent upon said-means to cut out said auxiliary resistance.

3. In a starter for electric motors, the combination with amotor, of astarting resistance normally cut out, an auxiliary resistance normallyin circuit with-a part of said motor, one or more members for varyingsaid starting resistance, said members -bemg normally out of thestarting position, electromagnetic means for moving said members fromrunning to starting position and to retard the movement ofsaid membersfrom starting to running position, and means controlled by saidelectromagnetic means for cutting out said auxiliary resistance whensaid members reach-the startingpos-ition.

4:. The cdmbination with an alternating current motor, of startingresistance therefor, auxiliary starting resistance, means for insertinsaid first-named resistance in circuit wit the rotor of the motor, andapparatus co-acting with said inserting means for cuttlng out saidauxiliary resistance, said inserting means effecting the gradual cuttingout of said first-named starting resistance as the motor increases inspeed. a

In motor controlling apparatus, the combination with an alternatingcurrent motor and a starting resistance connected to the rotorthereof,of one or more resistance-varying members normally cutting out saidresistance, auxiliary resistance normally in circuit with the rotor,electromagnetic means for moving said members from normal position tostarting position, and retarding the movements of said members fromstarting to running position, and appliances for cutting out saidauxiliary resistance after the -appliances controlled by said means forcutting out said auxiliary starting resistance.

7. In motor-controlling apparatus, the combination with analternatingcurrent'motor, of starting resistance connected to the rotor thereof,resistance-varying members normally shortcircuiting said resistance,auxiliary starting resistance normally in circuit, electromagnetic meansoperated upon the application of current to the motor to move saidresistance-varying members from normal to starting position, andappliances controlled by said means forcutting out said auxiliaryresistance, said means also retarding the automatic movements of saidmembers from starting to running position to effect a gradual cuttingout of said starting resistance.

8. In mdtor controlling apparatus, the combinatiqnwi'th an alternatingcurrent motor, of sta gting resistance connected to the retor thereofianauxiliary startin gji'esistance, a resistance contact-.member normallyin the running. position, said member bein movable from the runningposition to the starting position and automatically from the startingposition to the running position, electro-' magnetic means operated uponthe motor receivingcurrent for moving said resistance contact member tostarting position and for retarding its movement toward the runningposition,"and appliances operated upon said member reaching startingposition for cutting out said auxiliary resistance.

9. In motor-controlling apparatus, the combination with analternatinggcurrent Inotor, of a main starting resistance, an auxwhen inits initial position, an auxiliary means for inserting said resistancein cirfrom running to startingposition, and re ta'rdmg the movement ofsaid member autothe motor attaining a predetermined speed,

iliary starting resistance, a resistance contact member normally in therunning position, electromagnetic means operated by alternating currentfor moving said member matically from starting position to runningposition, and automatic mechanism for controlling said auxiliarystartingresistance.

10. In motor-controlling apparatus, the combination with an alternatingcurrent motor, a main starting resistance connected to the rotorthereof, an auxiliary starting resistance connected thereto, one or moreresistance contact members normally in the running position andshort-circuiting-said main starting resistance, electromagnetic meansoperated by alternating current for moving said members fromnormal tostarting position. and for retarding the automatic movements of saidmembers from starting to running position, and mechanism for controllingsaid auxiliary resistance.

11. In motor-controlling apparatus, the combination with a main startingresistance for an alternating current motor, of an auxiliary startingresistance, one or more switches normally short-circuiting said mainresistance, and electromagnetic means operated by alternating currentfor opening said switches and for automatically permitting thesuccessive closure of said switches to eifect a gradual cutting out ofsaid resistance, and mechanism dependent upon the opening of saidswitches for cutting out said auxiliary resistance. g

12. In motor-controlling apparatus, the combination with an alternatingcurrent motor, of main starting resistance therefor, auxiliary startingresistance, one or more switches normally short-circuiting said mainresistance, one or more single-phase magnets, one for operating each ofsaid switches to initially insert said main resistance and thereaftergradually cut out the same to effeet the acceleration of the motor, andmechanism automatically operated upon the opening of all of saidswitches for cutting out said auxiliary resistance.

13. In motor-controlling apparatus, the combination with an alternatingcurrent motor, of a main startingresistance therefor, resistance-varying,member or members normally short-circuiting said resistance startingresistance, and electromagnetic cuit with the rotor of the motor uponapplication of current to the motor, andto automatieally ---permit saidmember to again short-circuit said starting resistance upon andmechanism automatically operated after J all the main startingresistance is inserted to combination'with an alternating current motor,of motorcircuits therefor, a main startmg resistance connected to apartof the motor, one or more contact members movable in two directions tovary said resistance, an auxiliary starting resistance, electromagneticmeans operated upon the motor circuits receiving current to move saidresistance-varying member in one directionand to permit the 'same tomove in the opposite direction when the motor, attains a predeterminedspeed, and appliances dependent upon the insertion of all of said mamstarting resistance for cutting out said auxiliary resistance.

15. In IDOIJOIFCOIItIOHIIIg apparatus the combination with analternating current motor, of starting resistance therefor, one or moreacceleratlng magnet switches for controlling said starting resistance,auxiliary starting resistance, an electromagnetic switch for cutting outsaid auxiliary resistance, and means operated by one of the acceleratingmagnets for controlling the auxiliary resistapce magnet switches.

16. In motor-controlling apparatus, the

combination with an alternating current motor, of startm resistancetherefor, electro magnetic acce crating switches for controlling saidstarting resistance, said'starting resistance being normallyshort-eireuited by said switches, a plurality of auxiliary resistanccsconnected in circuit with a part of the motor, a double electromagneticswitch for cutting out said auxiliary resistances, an additionalresistance in circuit with the electromagnet of said last-named switch,and an additional switch operated by one of the accelerating magnets toshort-circuit said additional resistance to permit the saidclectromagnetic double switch to cut out said auxiliary resistances.

17. In motor-controlling apparatus, the combination with an electricmotor, of starting resistance therefor, accelerating magnet switchesnormally short-circuiting said resistance, auxiliary resistancesnormally con-' neeted to a part of the motor, and means dependent uponthe operation of the accelerating switches for cutting out saidauxiliary resistances.

18. In motor-controlling apparatus, the combination with an electricmotor, of starting resistance connected to a part of said motor, one ormore switches normally short-circuiting said resistance, electromagnetsfor opening said switches to insert said resistance upon the applicationof current to the motor, auxiliary resistances normally in circuit withsaid part of the motor, auxiliary switches for controlling saidauxiliary rev connected. to said last-named electromagnet I applied tothe motor, and an additional switch sistances, an electromagnet foroperating said theswitches actuated thereby to gradually auxiliaryswitches, an additional resistance short-circuit said startingresistance to effect the acceleration of the motor.

In testimony whereof, I have signed my 15 name to this specification inthe'presence of two subscribing witnesses.

JOHN D. IHLDER.

toprevent its operation when current is first operated upon theinsertion of thestarting resistance to short-circuit said additionalre-' sistance and permit the second-named .el'ectroniagnet to operatesaid auxiliary switches I and short-circuit said auxiliary resistances,said first-named electromagnets permitting.

Witnesses:

RUDOLPH C. SMITH, J. HALL KINSLEY.

